Three properties of ink leading to emulsification

Ink has three properties related to emulsification, namely the acid value of the ink, the viscosity of the ink, and the properties of the pigment.

(1) Acid value of the ink: The acid value of the ink pendant indicates the content of free fatty acid in the binder. Free fatty acid is also a typical surfactant. During emulsification, the hydrophilic group of fatty acid faces water, and the hydrophobic group faces oil, forming a water-in-oil emulsion. The polarity of the ink is often measured by the acid value of the binder. The more free fatty acids in the ink, the stronger the polarity of the ink and the more serious the emulsification. At the same time, the higher the acid value, the thicker the dampening diluent is required, which will promote emulsification. Therefore, the interfacial tension coefficient at the interface between ink and water often depends on their polarity difference. If the polarity of the fountain solution takes a certain value, and the polarity of water is greater than that of oil, then the greater the polarity of the ink, the smaller the polarity difference, and the easier it is to emulsify.

(2) Viscosity of the ink: The viscosity of the continuous medium plays an important role in the formation of a stable emulsion. In printing production, the viscosity of the ink is the main factor for emulsification, regardless of the viscosity, it can produce different degrees of emulsification. The viscosity spectrum of the ink is large, and its cohesion increases accordingly, which improves the water resistance from the surface. Therefore, the ink is added with О varnish. Can reduce emulsification. The viscosity of the oil is too small, the fluidity increases and the cohesion is weakened, which reduces the water resistance and is easy to emulsify. Therefore, it is not allowed to add No. 6 varnish arbitrarily in production to reduce the viscosity of the ink and increase the fluidity. Under normal circumstances, ink viscosity is inversely proportional to emulsification, and fluidity is directly proportional to emulsification.

(3) The nature of the pigment: the pigment is hydrophilic and hydrophobic, and the reason for its emulsification depends on the wettability of oil and water to the pigment. Practice has proved that the emulsification value of inks made of pigments with different properties varies greatly. For example: carbon black is a hydrophobic powder, so the emulsification value of the black circle is small; the emulsification value of the crimson prepared by Yili Sol Dahong is also small. However, the inks prepared from various ordinary lake pigments, because their raw materials are hydrophilic powders such as aluminum hydroxide, aluminum barium white, etc., the fast lakes also have certain hydrophilicity. When these inks come into contact with the fountain solution, once the structure of the ink is destroyed, the pigment particles may form an oil-in-water emulsion. Therefore, inks such as peacock blue, light red, green lotus, and light blue are easier to emulsify than black ink and red ink. In addition, the degree of emulsification of pigments varies, which can also be indirectly known from the water content and oil absorption of pigments.